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2024-09-04
Causes and countermeasures of weld corrosion
Generallyspeaking,puremetalmaterialswithasinglecomponentarenoteasytorust.Forordinarymetalironparts(processed),theyarepronetorustinhumidair;whileapieceofpureiron......
① In general, pure metal materials with a single component are not easy to rust. For ordinary metal iron parts (processed), it is easy to rust in humid air; while a piece of pure iron will not rust even if placed in water. The welding part of stainless steel is spliced by welding rods, which is a heating process, resulting in impure iron elements. When it encounters moisture and oxygen in the air, it is easy to rust.
② The method of stainless steel welding processing also has a certain influence on the rust of stainless steel materials. If a metal sheet is folded, it is easy to rust at the fold after being knocked to correct the flatness.
③ The smoothness of the metal surface is also related to the probability of rust. Smooth metal surfaces are not easy to rust, while rough metal surfaces are more likely to rust. Local overheating of the metal surface or external force knocking processing causes the surface temperature to rise, which is also one of the reasons for the rust of the metal surface.
How to deal with rust at the welding part of stainless steel?
① Surface polishing
The roughness of the welding part of stainless steel is large and there may be welding stains on the surface, which will accelerate the oxidation and rust of the welding surface. If the stainless steel weld is polished, the anti-oxidation ability of the weld surface can be improved, because the smaller the roughness of the metal surface, the better the corrosion resistance.
Because the surface of the polished stainless steel weld can produce a dense and uniform oxide film, it protects the internal metal and reduces the chance of oxidation corrosion
② Pickling and passivation treatment
1) The purpose of pickling is to first clean the oxide of the stainless steel weld. There are two methods of pickling: acid pickling and acid paste pickling. Common pickling liquids are sulfuric acid, nitric acid, hydrochloric acid, etc., but these pickling liquids are difficult to meet environmental protection requirements, so more and more pickling and rust removal will choose organic acids (recommended vci-708 environmentally friendly rust remover, no acid mist, will not cause excessive corrosion to stainless steel parts, and the rust removal rate is fast)
2) The purpose of passivation is to produce a dense oxide film on the metal surface to increase the surface's ability to resist corrosion and oxidation. The process of passivation treatment is:
Weld surface cleaning and repair → pickling → water washing and neutralization → passivation → water washing and drying
3) For neutralization after pickling, alkaline metal surface cleaning agents can be used for treatment. It can not only neutralize the pickling residual liquid on the surface after pickling, but also clean the dust and human sweat residue on the surface. (Recommended biodegradable and environmentally friendly metal cleaning agent: vci-600E metal cleaning agent)
In fact, for the problem of rust on stainless steel welding, a series of protective operations can be performed during welding to reduce the risk of oxidation. In addition to removing the surface oxides, the surface can also be treated with anti-rust treatment, and if necessary, anti-rust protection can be added to the stainless steel weldment during storage and transportation (vapor phase anti-rust film, vapor phase anti-rust paper, anti-rust desiccant, etc. can be used for protection)
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